At the beginning of the week, on Nov. 24, hackers calling themselves Guardian of Peace took over computers at the studio, forcing it to shut down its email and other systems. The studio has hired FireEye Inc.’s Mandiant forensics unit to restore service, Reuters reported Sunday evening, with hopes of bringing its systems back online by Monday. Throughout the weekend, though, at least some of the emails sent to studio addresses continued to bounce back, with the message that the studio’s email system was “currently experiencing a disruption,” and studio execs took to using private emails to disseminate the weekend grosses.